diff --git a/programs/x509/cert_write.c b/programs/x509/cert_write.c
index 9776dc1..aa70a17 100644
--- a/programs/x509/cert_write.c
+++ b/programs/x509/cert_write.c
@@ -310,7 +310,6 @@
     mbedtls_ctr_drbg_context ctr_drbg;
     const char *pers = "crt example app";
     mbedtls_x509_san_list *cur, *prev;
-    mbedtls_asn1_named_data *ext_san_dirname = NULL;
     uint8_t ip[4] = { 0 };
     /*
      * Set to sane values
@@ -593,7 +592,12 @@
                     cur->node.san.unstructured_name.len = sizeof(ip);
                 } else if (strcmp(q, "DN") == 0) {
                     cur->node.type = MBEDTLS_X509_SAN_DIRECTORY_NAME;
-                    if ((ret = mbedtls_x509_string_to_names(&ext_san_dirname,
+                    /* Work around an API mismatch between string_to_names() and
+                     * mbedtls_x509_subject_alternative_name, which holds an
+                     * actual mbedtls_x509_name while a pointer to one would be
+                     * more convenient here. */
+                    mbedtls_asn1_named_data *tmp_san_dirname = NULL;
+                    if ((ret = mbedtls_x509_string_to_names(&tmp_san_dirname,
                                                             subtype_value)) != 0) {
                         mbedtls_strerror(ret, buf, sizeof(buf));
                         mbedtls_printf(
@@ -602,7 +606,9 @@
                             (unsigned int) -ret, buf);
                         goto exit;
                     }
-                    cur->node.san.directory_name = *ext_san_dirname;
+                    cur->node.san.directory_name = *tmp_san_dirname;
+                    mbedtls_free(tmp_san_dirname);
+                    tmp_san_dirname = NULL;
                 } else {
                     mbedtls_free(cur);
                     goto usage;
@@ -994,7 +1000,6 @@
 #if defined(MBEDTLS_X509_CSR_PARSE_C)
     mbedtls_x509_csr_free(&csr);
 #endif /* MBEDTLS_X509_CSR_PARSE_C */
-    mbedtls_asn1_free_named_data_list(&ext_san_dirname);
     mbedtls_x509_crt_free(&issuer_crt);
     mbedtls_x509write_crt_free(&crt);
     mbedtls_pk_free(&loaded_subject_key);